This invention relates to monitoring the operation of an internal combustion engine. More particularly, it relates to a method of monitoring the operation of such an engine and to a monitoring device for use in such method.
The invention finds particular application in the monitoring of a vehicle engine during driving, for purposes of promoting driving habits which result in economic utilization of fuel, and providing vehicle fleet operators with a management tool for use in monitoring the driving habits of drivers.
Applicant is aware of a warning device for use in a vehicle having an internal combustion engine, which device comprises a diaphragm type actuator arranged to actuate an electrical switch. The switch is connected in series with an electrical warning light to a source of electric current, and the diaphragm type actuator is connected to the inlet manifold of the engine. The operation of the device is such that, when the degree of vacuum in the inlet manifold falls below a predetermined value, the switch is closed, causing the warning light to be actuated. This will then be an indication to the driver of the vehicle that the engine operating conditions are such as to lead to uneconomic utilization of fuel.
Applicant is also aware of a device for use in a vehicle having an internal combustion engine, which device comprises a diaphragm type actuator and a mechanically operated counting device arranged to be acted upon mechanically by the diaphragm type actuator when the degree of vacuum in the engine's inlet manifold falls to below a predetermined value, to record a count on the counter.
Applicant has found that when the devices referred to above are adjusted to provide a warning signal or a recording when the degree of vacuum falls to a value at which there is uneconomic utilization of fuel, at low engine speeds, then the driver is able, by gradually increasing the speed of the vehicle, to obtain a relatively high speed without a warning signal being issued or a recording being made. At such high speeds there is again uneconomic utilization of fuel. However, if the devices are adjusted to provide a warning signal or a recording when there is uneconomic utilization of fuel at high engine speeds, then the devices become so sensitive at low engine speeds that the slightest acceleration results in a warning signal being issued or a recording being made. This is frustrating to the driver and inhibits smooth traffic flow.
Another disadvantage of the device described above having a mechanical counter is that it provides a single count whenever the degree of vacuum falls below the predetermined value, regardless of the length of time for which the degree of vacuum remains below that value. The reading on the counter will therefore be of little value to a fleet operator, as the driver can keep the reading on the counter at a low value by driving in such a manner that the degree of vacuum in the inlet manifold remains at low, uneconomical levels for long stretches of time.